1. Field of the Invention
The present disclosure is related to the field of laser diodes and, in particular, to a low-side laser diode driver with laser diode array protection and power efficiency monitoring and adjustment.
2. Discussion of Related Art
In order to pump single and/or multiple light-coupled laser gain media to high output light powers, high-current, e.g., one hundred amperes or more, laser diode arrays are typically required as the sources of pump light for the various laser gain media. These laser diodes are expensive and are very sensitive to signal or chassis ground shorts anywhere in the series laser array diode chain. Since these expensive laser diodes are usually tightly coupled to a chassis heat sink to lower their junction temperature, the probability of a chassis ground short to either the anode or cathode of the diode in question is a possibility.
A solution to laser diode array ground shorts is the use of high-side linear constant current sources or high-side switch-mode constant current sources. In these systems, when a short occurs, the high-side current source continues to pump the commanded high-side current pulses through the laser diodes above the short and then into the ground short and back to the return of the high-side current source. In these configurations, the laser diodes will not be damaged because the high-side current source continues to pump only the constant current pulses initially programmed. The laser diodes below the ground short cease to conduct any current at all.
There are at least three drawbacks to the high-side current source approach. Once a ground short occurs, the high-side driver continues to pump the high-current pulses even though the system has failed. Typically, the user is not immediately aware that a failure has occurred by looking at the high-side current source alone, unless some other failure detection system is present. The second drawback is that high-side drive is significantly more complex than the simpler linear low-side constant current sink approach. The third drawback is that, if the ground short occurs near the top of the diode string, most all of the input voltage appears across the high-side current source, thus greatly increasing the power dissipation within the high-side current source and potentially causing high-side current source failure.